Water-based hydraulic fluids comprising dithio-di(aryl carbolic acids)

Abstract

The invention relates to water-based hydraulic fluids comprising a) water, b) at least one glycol, a polyglycol, or both, and c) 0.1 to 30 wt % of at least one compound of formula 1, where M is hydrogen, an alkali metal, an alkali earth metal, or ammonia, Ar 1 and Ar 2 are independently monocyclic or polycyclic aromatic groups that can have substituents or can comprise heteroatoms.

The invention claimed is: 
     
       1. A hydraulic fluid comprising
 a) water, 
 b) at least one glycol, a polyglycol or both, and 
 c) from 0.1 to 30% by weight of at least one compound of the formula 1 
 
       
         
           
           
               
               
           
         
       
       wherein
 M is hydrogen, alkali metal, alkaline earth metal or ammonium, 
 Ar 1  and Ar 2  are each independently mono- or polycyclic aromatic groups which may bear substituents or may contain heteroatoms, and wherein the Ar 1  and Ar 2  radicals each have only one substituent which is not H apart from the carboxyl group and the sulfide bridge. 
 
     
     
       2. The hydraulic fluid as claimed in  claim 1 , containing 35-70% by weight of water and 25-50% by weight of a glycol, of a polyglycol or both. 
     
     
       3. The hydraulic fluid as claimed in  claim 1 ,
 wherein Ar 1  and Ar 2  are each groups of the formulae 2a-2c 
 
       
         
           
           
               
               
           
         
         wherein R 1 , R 2 , R 3 , R 4  are each independently H, CH 3 , C 2 -C 20 -alkyl or -alkenyl, C 3 - to C 20 -cycloalkyl, halogen, NO 2 , NO 3 , CN, OX, NH 2 , NHX or N(X) 2 , 
         where X=C 1 -C 20 -alkyl or C 3 - to C 20 -cycloalkyl. 
       
     
     
       4. A hydraulic fluid comprising
 a) water, 
 b) at least one glycol, a polyglycol or both, and 
 c) from 0.1 to 30% by weight of at least one compound of the formula 1 
 
       
         
           
           
               
               
           
         
       
       wherein
 M is hydrogen, alkali metal, alkaline earth metal or ammonium, and 
 wherein each of the Ar 1  and Ar 2  radicals are monocyclic aromatic radical of the formula 3 
 
       
         
           
           
               
               
           
         
         wherein the free valence indicates the position of the sulfide bridge, and X is a C 1 - to C 4 -alkyl group, a nitro group or a halogen atom. 
       
     
     
       5. The hydraulic fluid as claimed in  claim 4 , wherein X is in the para position to the sulfide bridge. 
     
     
       6. The hydraulic fluid as claimed in  claim 4 , wherein X is a methyl or ethyl group. 
     
     
       7. The hydraulic fluid as claimed in  claim 1 , wherein the formula 1 is dithiodibenzoic acid. 
     
     
       8. The hydraulic fluid as claimed in  claim 1 , further comprising at least one further anticorrosive selected from the group consisting of
 a) toluene- or benzenesulfonamidocaproic acids of the formula 6 
 
       
         
           
           
               
               
           
         
         
           where R 5 , R 6 =H or CH 3 , 
         
         b) isononanoylamidocaproic acid of the formula 7 
       
       
         
           
           
               
               
           
         
       
       and
 c) triazinetrisaminohexanoic acid of the formula 8 
 
       
         
           
           
               
               
           
         
       
     
     
       9. The hydraulic fluid as claimed in  claim 1  further comprising at least one further anticorrosive selected from the group consisting of the aliphatic and aromatic carboxylic acids, the aliphatic and aromatic dicarboxylic acids, the aliphatic and aromatic polycarboxylic acids, the phthaiic monoamides, alkanesulfonamides and the alkanesulfonamidocarboxylic acids. 
     
     
       10. The hydraulic fluid as claimed in  claim 1 , further comprising a lubricant for reducing friction and abrasion. 
     
     
       11. The hydraulic fluid as claimed in  claim 1 , further comprising a neutralizing agent selected from the group consisting of the amines, alkanolamines, alkali metal hydroxides and oxides, and alkaline earth metal hydroxides and oxides. 
     
     
       12. The hydraulic fluid as claimed in  claim 1 , further comprising a freezing point depressant selected from the group consisting of the ethylene glycols, propylene glycols, alkyl glycols, and alkylpropylene glycols. 
     
     
       13. The hydraulic fluid as claimed in  claim 1 , further comprising a thickener selected from the group consisting of the polyacrylates, polymethacrylates, polyethylene glycols, polypropylene glycols, and polyalkylene glycols. 
     
     
       14. A process for improving the anti-corrosivity or lubricity of a hydraulic fluid, wherein the hydraulic fluid comprises water and at least one glycol, at least one polyglycol or mixtures thereof, comprising the step of adding from 0.1 to 30% by weight of a compound of the formula 1 
       
         
           
           
               
               
           
         
       
       in which
 M is hydrogen, alkali metal, alkaline earth metal or ammonium, 
 Ar 1  and Ar 2  are each independently mono- or polycyclic aromatic groups which may bear substituents or may contain heteroatoms, and wherein the Ar 1  and Ar 2  radicals each bear only one substituent which is not H apart from the carboxyl group and the sulfide bridge to the hydraulic fluid. 
 
     
     
       15. The hydraulic fluid as claimed in  claim 4 , further comprising at least one further anticorrosive selected from the group consisting of
 a) toluene- or benzenesulfonamidocaproic acids of the formula 6 
 
       
         
           
           
               
               
           
         
         
           where R 5 , R 6 =H or CH 3 , 
         
         b) isononanoylamidocaproic acid of the formula 7 
       
       
         
           
           
               
               
           
         
       
       and
 c) triazinetrisaminohexanoic acid of the formula 8 
 
       
         
           
           
               
               
           
         
       
     
     
       16. The hydraulic fluid as claimed in  claim 4 , further comprising at least one further anticorrosive selected from the group consisting of the aliphatic and aromatic carboxylic acids, the aliphatic and aromatic dicarboxylic acids, the aliphatic and aromatic polycarboxylic acids, the phthalic monoamides, alkanesulfonamides and the alkanesulfonamidocarboxylic acids. 
     
     
       17. The hydraulic fluid as claimed in  claim 4 , further comprising a lubricant for reducing friction and abrasion. 
     
     
       18. The hydraulic fluid as claimed in  claim 4 , further comprising a neutralizing agent selected from the group consisting of the amines, alkanolamines, alkali metal hydroxides and oxides, and alkaline earth metal hydroxides and oxides. 
     
     
       19. The hydraulic fluid as claimed in  claim 4 , further comprising a freezing point depressant selected from the group consisting of the ethylene glycols, propylene glycols, alkyl glycols, and alkylpropylene glycols. 
     
     
       20. The hydraulic fluid as claimed in  claim 4 , further comprising a thickener selected from the group consisting of the polyacrylates, polymethacrylates, polyethylene glycols, polypropylene glycols, and polyalkylene glycols. 
     
     
       21. A process for improving the anti-corrosivity or lubricity of a hydraulic fluid, wherein the hydraulic fluid comprises water and at least one glycol, at least one polyglycol or mixtures thereof, comprising the step of adding from 0.1 to 30% by weight of a compound of the formula 1 
       
         
           
           
               
               
           
         
       
       in which
 M is hydrogen, alkali metal, alkaline earth metal or ammonium, 
 and wherein each of the Ar 1  and Ar 2  radicals are a monocyclic aromatic radical of the formula 3 
 
       
         
           
           
               
               
           
         
         wherein the free valence indicates the position of the sulfide bridge, and X is a C 1 - to C 4 -alkyl group, a nitro group or a halogen atom to the hydraulic fluid.